Reduction of electric-field-induced damage in field-sensitive articles

ABSTRACT

A continuously electrically-conductive container ( 104 ) contains an electrically-insulating support ( 110 ) for holding an electric-field-sensitive article ( 112 ), such as a reticle, so that the article is shielded from external electric fields and is not in electrical contact with a conductive container wall ( 106 ). A SMIF pod ( 302, 510 ) comprises an electrically conductive container for holding an electric-field-sensitive article. A system ( 502 ) has boundary walls ( 504 ) that form a chamber ( 506 ) for a controlled environment. The system includes a load port ( 508 ) for receiving a SMIF pod and an end effector ( 522 ) made of insulating material for moving a field-sensitive article ( 516 ) within the chamber to and from the SMIF pod. An ionizer ( 542 ) neutralizes electric charges on the field-sensitive article.

FIELD OF THE INVENTION

This invention relates to the field of controlling and reducingelectric-field-induced damage during integrated circuit fabrication and,in particular, to protection against electric-field-induced damage inreticles.

BACKGROUND OF THE INVENTION

Statement of the Problem

Certain objects in semiconductor manufacturing, such as packageddevices, silicon wafers and reticles are prone to damage byfield-induced potentials. A reticle is an optically clear ceramicsubstrate (typically quartz) having a thin metal (e.g., chromium)coating in which a pattern has been formed. Field-induced damage canoccur even without any electrical contact being made with the sensitiveobject. The mechanism of damage has been widely identified as resultingfrom electrostatic discharge (ESD), a mechanism that occurs when thevoltage between electrically isolated parts within a device or object israised by field induction to a point at which a discharge occurs betweenthem. There is a threshold for the occurrence of such discharge, belowwhich the risk of damage is considered to be small. The variousthresholds for discharge in different types of object have beenestimated and “safe” levels for electric field around them have beenprescribed in several places, such as the International TechnologyRoadmap for Semiconductors.

Much of the information available about static control was developed forspark avoidance where there is an explosion risk, such as in thehandling of flammable liquids and vapors. Spark avoidance has also beena priority in semiconductor manufacturing since the radio emissions fromspark events can cause data corruption in the electronics used tocontrol process equipment.

To minimize the risk of ESD, it is common practice to control staticcharge levels in the environments where field-sensitive objects arehandled. The guidance given by bodies such as the ESD Association ofAmerica for the control of ESD includes the avoidance of all insulatorsthat are not necessary for the process, the use of static dissipativematerials wherever the use of metal is inappropriate (e.g., fortransparency or chemical inertness), and electrical grounding of allconductive or dissipative parts of the equipment through a common groundpoint. It is common practice to control static charge levels in handlingenvironments. For example, grounded static dissipative materials areused in semiconductor manufacturing facilities (herein “fabs”) tominimize tribocharging of reticle pods and other handling equipment.

Electrostatic buildup on and discharge from reticles can damage ordestroy the reticles, and concern about electrostatic damage has beenincreasing in recent years as device geometries get finer and therequirements for reliability become more stringent.

It is known to store and transfer workpieces, such as semiconductorwafers and reticles, using a standard mechanical interface, or SMIF,system. In conventional SMIF pods, it is known to have conductivecontacts on the reticle support in the pod door to dissipateelectrostatic charge from the bottom surface of the reticle. The chargeis then grounded through the pod door. Similarly, conductive contactsare provided on the reticle retainer in the pod shell to dissipateelectrostatic charge from the top surface of the reticle. The chargefrom the top surface is then grounded through the pod shell. The podshell, therefore, typically includes static dissipative materials toprovide a path to ground for the static charge from the top surface ofthe reticle. Another type of reticle container provides a conductivepath between the reticle retainer and the reticle supports, as disclosedin U.S. Pat. No. 6,513,654, issued Feb. 4, 2003, to Smith et al. Thisallows electrostatic charge to be dissipated from the top surface of thereticle without the use of static dissipative materials in the podshell.

Field-sensitive objects often carry electrical charge. An object canacquire a charge through tribocharging during handling, through normalprocessing such as rinsing with deionized water, through ionizermalfunction and by other events. Not all such situations can be avoided,particularly when charging is an unfortunate by-product of the processitself (such as washing). It is known to provide air ionizers toneutralize electric charges on objects.

SUMMARY OF THE INVENTION

The present invention helps to the problems outlined above by providingapparati, systems and methods for avoiding electric-field-induced damageto field-sensitive articles.

A first basic embodiment of an apparatus in accordance with theinvention for holding a field-sensitive article comprises a conductivecontainer having an electrically-conductive container wall that definesan enclosure. A conductive container functions as a Faraday cage bysubstantially preventing an external electric field from passing throughthe conductive container wall. As a result, the external electric fieldhas no influence in the enclosure within the conductive container or inany objects within the container. Typically, the electrically-conductivecontainer wall comprises substantially only conductive material, but theconductive container wall can also be made from non-conducting materialthat is coated or embedded with conductive material to make the wallelectrically conducting. Another important element of an apparatus inaccordance with the invention is an electrically-insulating supportlocated within the enclosure. The electrically-insulating support isconfigured for supporting a field-sensitive article within the enclosureso that the field-sensitive article is not in electrical contact withthe electrically-conductive container wall or with other conductive orstatic dissipative objects. By keeping the field-sensitive articleelectrically isolated and distant from the conductive wall of thecontainer (Faraday cage), an apparatus in accordance with the inventionfurther protects a field-sensitive article, such as a reticle, that ispossibly carrying an electric charge before it is moved into theconductive container against the risk posed by a charged object being inclose proximity to a fixed-potential surface. Conventional systems ofthe prior art typically support the reticle on static dissipativesupports. Preferably, an electrically-insulating support in accordancewith the invention comprises substantially only insulative material;such as insulative ceramic or polymer plastic material.

A conductive container in accordance with the invention usually isconnected to a controlled potential, preferably a fixed potential, suchas electrical ground. Certain embodiments include a distinct controlledelectrical potential connected to the conductive container. Accordingly,certain embodiments comprise an electrical connector, such as anelectrical conductor or a static dissipative connector, connecting theconductive container to a controlled electrical potential.

In some embodiments, a conductive container is a portion of a SMIF pod.In some embodiments, the electrically-insulating support within theenclosure of the container is configured for supporting a reticle. Anapparatus in accordance with the invention optionally includes anionizer located external to the enclosure for neutralizing an electriccharge. It is located within the chamber to neutralize charges thatmight be on a field-sensitive article before or after it is placed inthe enclosure of the container, as well as neutralize charges that mightbe on insulative internal structures in the chamber or within theconductive container. In some embodiments, a portion of theelectrically-conductive container wall is substantially transparent.

Another basic embodiment comprises a system for handling afield-sensitive article. The system includes boundary walls, a chamberdefined by the boundary walls, a load port for holding and operating aSMIF pod, a SMIF pod, and an effector for moving an article within thechamber to or from an open SMIF pod. In accordance with the invention,the SMIF pod comprises a conductive container and anelectrically-insulating support located within the conductive container.The electrically-insulating support is configured for supporting afield-sensitive article without electrical contact to the conductivecontainer. The effector is an electrically-insulating effectorconfigured for moving a field-sensitive article. Some embodimentsfurther include an electrically-insulating chamber-internal supportconfigured for supporting a field-sensitive article within the chamberwithout electrical contact to the boundary walls. In preferredembodiments, electrically-insulating structures located within thechamber boundary walls, such as the electrically-insulatingchamber-internal support, comprise substantially only insulativematerial. Some embodiments further comprise an electrically-insulatinginternal panel located within the chamber. Preferably, theelectrically-insulating internal panel comprises substantially onlyinsulative material. In some embodiments, the boundary walls aresubstantially electrically conductive, often being made fromelectrically conductive material. In other embodiments, the boundarywalls are mainly static dissipative. In preferred embodiments of thesystem, the boundary walls are connected to a controlled electricalpotential or to electrical ground. In some embodiments, theelectrically-insulating support is configured for supporting a reticleand the effector is configured for moving a reticle. Some systems inaccordance with the invention further an ionizer located within thechamber for neutralizing a electric charges. To provide visibility intothe system, some embodiments include at least a portion of the boundarywalls that is substantially transparent.

Still another basic embodiment for handling a field-sensitive includesboundary walls, a chamber defined by the boundary walls, and a containerwithin the chamber for holding a field-sensitive article. The containercomprises an electrically-conductive container wall in accordance withthe invention that defines an enclosure. The system also includes anelectrically-insulating support located within the enclosure andconfigured for supporting a field-sensitive article within the enclosureso that the field-sensitive article is not come into electrical contactwith the electrically-conductive container wall or with other conductiveor static dissipative objects. The system further includes an ionizerfor providing charge-neutralizing ions in the chamber.

A method of avoiding field-induced damage of a field-sensitive articleincludes holding the field-sensitive article with anelectrically-insulating support located within an enclosure defined byan electrically-conductive container wall of a conductive container sothat the field-sensitive article does not electrically contact theelectrically-conductive container wall. Some methods in accordance withthe invention further include locating the conductive container in achamber having a controlled environment, generating ions in thecontrolled environment in the chamber, and opening the conductivecontainer in the controlled environment. Some embodiments in accordancewith the invention include locating the conductive container in achamber having a controlled environment, then opening the conductivecontainer in the controlled environment, and then moving thefield-sensitive article out of the conductive container into thecontrolled environment using an electrically-insulating effector.

Thus, a field-sensitive article is protected from the effects ofexternally generated electric fields and also from the effects of beingelectrically charged, which might occur during handling.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the invention may be obtained byreference to the drawings, in which:

FIG. 1 schematically depicts a cross-sectional view of a generalizedbasic embodiment of an apparatus in accordance with the invention forholding a field-sensitive article;

FIG. 2 depicts schematically an enlarged portion of FIG. 1 showing fieldcontours in the vicinity of an electric charge on a reticle;

FIG. 3 depicts schematically field contours in the vicinity of anelectric charge on a reticle supported by a conventional conductive ordissipative support of the prior art;

FIG. 4 depicts a perspective view of a SMIF pod for holding afield-sensitive reticle in accordance with the invention;

FIG. 5 depicts a cross-sectional view of a SMIF pod in a closed positionholding a field-sensitive reticle;

FIG. 6A depicts a perspective view of a cassette portion of amulti-reticle SMIF pod;

FIG. 6B depicts a perspective view of a cover portion of a multi-reticleSMIF pod;

FIG. 7 depicts schematically a cross-sectional view of a system inaccordance with the invention containing a SMIF pod, a load port and acontrolled environment;

FIG. 8 shows a schematic view of the system of FIG. 7 in which the SMIFpod is in an open position within the controlled environment;

FIG. 9 depicts field lines of an electric field between an electriccharge on an article and boundary walls at a different electricalpotential, such field lines being largely unperturbed by the insulativeeffector and insulative internal panels in accordance with theinvention;

FIG. 10 depicts a system in accordance with the invention comprising anionizer for neutralizing electrical charges on a field-sensitive articleand on insulative panels and other internal structures;

FIG. 11 depicts a conventional system of the prior art that includes aneffector made from conductive or static dissipative material, not inaccordance with the invention; and

FIG. 12 depicts a conventional system of the prior art that includesinternal panels comprising conductive or static dissipative material,not in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention is described herein with reference to FIGS. 1-12. Itshould be understood that the structures and systems depicted inschematic form in FIGS. 1, 2, and 4-10 are used to explain the inventionand are not precise depictions of actual structures and systems inaccordance with the invention. Furthermore, processes are described inthe specification with reference to FIGS. 1, 2, 4-10; nevertheless, itis clear that methods in accordance with the invention can be practicedusing apparati very different from those depicted in FIGS. 1, 2, 4-10.The preferred embodiments described herein are exemplary and are notintended to limit the scope of the invention, which is defined in theclaims below.

Embodiments in accordance with the invention are described herein mainlywith reference to the handling of reticles. Is understood, however, thatthe invention is useful for protecting a wide variety of field-sensitivearticles, particularly in semiconductor manufacturing facilities.

Field-induced damage in reticles was previously attributed in the art tomultiple low-level ESD events, with voltages being around 150 volts formicron-sized gaps, lower than the minimum of approximately 350 voltspredicted by Paschen's Law for inner discharge and atmospheric pressure.Analysis of field-induced damage indicates that in addition to ESD,there are separate and more subtle damage mechanisms, which occursimultaneously as a result of field penetration into the mask imagearea. These damage mechanisms involve electric field-induced migration(“EFM”) of metal (typically chrome) onto the surface of a reticlesubstrate (typically quartz) between lines. These damage mechanisms takeplace at lower potential differences in the reticle than those thatcause ESD events. Field-sensitive articles have different sensitivity tofield-induced potentials. For example, the sensitivity of a reticledepends upon the length, spacing and density of the chrome lines in theimage area. The induced-voltage range that results in EFM damage isbelieved to begin at about 5 V for reticle line gaps of about 1 micron.As integrated-circuit feature dimensions become smaller, the sensitivityof reticles to ESD and EFM increases. EFM is a gradually operatingcumulative damage mechanism, so reticle degradation progressescontinually over time rather than occurring as a discrete event.

When a field sensitive object such as a reticle is transported within afab, it passes through many electrostatic hazards. Shielding fromexternally generated electric fields is a necessary part of theprotection of such an object. Shielding from electric fields is providedby placing a fully conductive enclosure around the object. As has beenexplained, however, bringing a fixed-potential object (such as agrounded container wall or a grounded effector) close to a chargedfield-sensitive article results in a strong electric field. Embodimentsin accordance with the invention help to reduce such risks.

FIG. 1 schematically depicts a cross-sectional view 100 of a generalizedbasic embodiment of an apparatus 102 in accordance with the inventionfor holding a field-sensitive article. Apparatus 102 includes aconductive container 104 having electrically-conductive container wall106. Container wall 106 defines an enclosure 108. Apparatus 102 furtherincludes an electrically-insulating support 110 configured forsupporting a field-sensitive article 112 within enclosure 108 in such amanner that field-sensitive article 112 does not come in contact withelectrically-conducted container wall 106.

Ideally, container wall 106 provides a continuous, integral conductivecontainer enclosing the space of enclosure 108, thereby enclosing afield-sensitive article 112 in a so-called Faraday cage. A containerwall that is not a continuous, integral conductive wall still providesprotection in the enclosure against electric fields external to thecontainer, but the degree of protection decreases as a container wallbecomes less integrally conductive. The material of container wall 106may comprise substantially only electrically conductive material.Alternatively or in combination with a substantially conductivematerial, container wall 106 may comprise insulative or staticdissipative material that functions as a support for a coating ofconductive material, or insulative or static dissipative materialembedded with conductive material, such as graphite or other conductiveparticles, or with an embedded metal mesh. Preferably, the conductivematerial is a conductive metal, such as stainless-steel-304 oraluminum-6061. Typically, container wall 106 comprises substantiallyonly a conductive metal, such as stainless steel 304.Stainless-steel-304 and other types of stainless steel are commonly usedin clean-room environments of integrated-circuit fabrication facilities(“fabs”). When container wall 106 comprises insulative or staticdissipative material coated with a conductive material, these materialsshould be selected to minimize outgassing into enclosure 108.

The term “conductive material” and related terms as used in thisspecification generally mean a material having a surface resistivity notexceeding approximately 1×10³ ohms per square and a volume resistivitynot exceeding approximately 1×10³ ohm-cm. The terms “insulativematerial”, “insulating material” and related terms are used in thisspecification generally mean material having a surface resistivity notless than about 1×10¹² ohms per square and a volume resistivity not lessthan about 1×10¹¹ ohm-cm. The term “static dissipative material”,“dissipative material” and related terms as used in this specificationgenerally mean a material having a surface resistivity in a range ofabout from 1×10³ to 1×10¹² ohms per square and a volume resistivity in arange of about from 1×10³ to 1×10¹¹ ohm-cm. The term “nonconductivematerial” and related terms in this specification generally means amaterial showing no significant conductive properties, that is, aninsulative material.

The term “electrically conductive” and related terms are used broadly inthis specification to refer to a material or to a structure that is, forexample, electrically conductive as defined above, or is coated with aconductive material.

The term “electrically insulating” and related terms are used broadly inthis specification to refer to a material or to structure that is, forexample, electrically insulating as defined above, or is coated with aninsulating material.

An electrically-conductive container in accordance with the inventionfunctions as a Faraday cage, effectively shielding the enclosure withina container from electric fields external to the container. An externalelectric field can arise in a variety of ways, for example, from anelectric charge or from alternating current.

A general objective of embodiments in accordance with the invention isto maintain a field-sensitive article 112 in enclosure 108 as far awayas possible from surfaces or conductive objects having a ground or otherelectrical potential. For this reason, electrically-insulating support110 preferably is made only from insulative material. Practically, anelectrically-insulating support 110 in accordance with the invention isphysically connected directly or indirectly with conductive containerwall 106. Nevertheless, as much as possible of anyelectrically-insulating support 110 proximate to a field-sensitivearticle 112 is made from electrically insulative material. As depictedin FIG. 1, apparatus 102 typically includes electrically-insulatinginternal panels 114. In the embodiment of apparatus 102, internal panels114 function as insulating side retainers or article-alignmentretainers. Ideally, all internal structures, such aselectrically-insulating support 110 and internal panels 114, that arelocated within enclosure 108 are made only from insulative material.When manufacturing or operational constraints do not practically allowan internal structure within enclosure 108 to be made from insulativematerial, then portions of such a structure that are in the closevicinity of a field-sensitive article 112 while it is supported onsupport 110 or being moved in or out of enclosure 108 should be madefrom insulative material. An electrically-insulating support and otherstructures located within the enclosure function in accordance with theinvention even when they comprise conductive material so long as afield-sensitive article only comes into contact withelectrically-insulating (insulative) material, for example, with anelectrical-insulator coating on the support or other internal structure.Nevertheless, the protection of a field-sensitive article is not as goodas when the support or other internal structure comprises onlyinsulative material.

Ideally, a field-sensitive article 112 does not come into closeproximity with other conductive surfaces. Therefore,external-electric-field-free enclosure 108 is designed to be as large aspossible within manufacturing and operational constraints. The designand locations of support 110, internal panel 114 and other structures inenclosure 108, and container openings (not shown) for moving an articleinto or out of enclosure 108 are implemented to minimize electric fieldeffects on a field-sensitive article 112.

When an electric charge, such as a static electric charge, exists on afield-sensitive article 112, then an electric field exists between thecharge on the article and the internal conductive features of thecontainer and any conductive structures within enclosure 108. The fieldgradient depends on the distance between the charged article andconductive container wall 106 and any conductive or static dissipativefeatures that are in electrical contact with container wall 106.Furthermore, the intensity of the electric field depends on the chargedistribution and the topography of both the field-sensitive article andthe internal conductive or dissipative surfaces of container 104. Anyprotrusions or sharp features on the internal conductive or staticdissipative surfaces of the container that might concentrate the fieldemanating from the charged article increase the risk of field-induceddamage, such as ESD and EFM. For this reason, internal structures 110,114 preferably are made only from insulative material, and conductivecontainer walls 106 preferably are smooth, without sharp protrusions andcorners. Conductive container wall 106 depicted in FIG. 1 has a smoothelliptical shape. It is understood that conductive container wall 106 inaccordance with the invention can have various shapes. It is also clearthat conductive wall 106 can be housed in a structure having a shapedifferent from container wall 106. Also, container wall 106 may compriseone or a plurality of sections that fit together to make a continuous,integral electrically-conductive container in accordance with theinvention.

Holding a field-sensitive article 112, such as a reticle, in anexternal-field-free enclosure 108 of a conductive container 106 oninsulating supports 110 does not increase the risk to the article beyondthe risk already posed by a) electrically charging it in the firstplace, and b) modifying the field pattern around the object by placingit within a grounded conductive or static dissipative container to allowthe object to be stored or transported in a stable environment to aplace where the charge that has been placed on the object can be safelyneutralized or dissipated.

A preferred embodiment of the invention includes a fully electricallyconductive container (Faraday cage), but the principle of protectionagainst field-induced damage of a charged article through electricalisolation also applies to a static dissipative container.

A reticle used for the production of semiconductor devices is an exampleof a field-sensitive article suitable for protecting in accordance withthe invention. A reticle is typically made of quartz or glass, andtypically has a size of about 15 cm by 15 cm height and width and athickness of about 6 mm. A reticle is coated on one side with adiscontinuous light-absorbing metallic film, typically chromium,surrounded by a continuous border of the metal, called the guard ring.Thus, a reticle comprises both insulating and conducting regions, thebulk of the reticle being insulative.

FIG. 2 depicts schematically an enlarged portion of “window” 120 ofFIG. 1. Window 120 in FIG. 2 shows conductive container wall 106,electrically-insulating support 110, field-sensitive reticle 112 locatedon support 110, and aligning side-retainer 114. Electrically-insulatingsupport 110 and side-retainer 114 comprise only electrically insulativematerial in accordance with preferred embodiments of the invention. Asdepicted in FIG. 2, a static electrical charge 122 is located on asurface of field-sensitive reticle 112. As a result, an electric fieldrepresented by electric-field contours 124 exists between charge 122 onreticle 112 and conductive wall 106, which is at ground potential.Because support 110 and side-retainer 114 comprise substantially onlyinsulative material, they do not significantly influence the electricfield present in enclosure 108.

FIG. 3 depicts a window 220 that shows a portion of a conventionalapparatus in the prior art having a grounded conductive or dissipativecontainer wall 206 that defines an enclosure 208, a grounded conductiveor dissipative support 210, and a grounded conductive or dissipativeside-retainer 214. An electric charge 222 is located on a reticle 212,causing an electric field represented by electric-field lines 224.Grounded support 210 and grounded side-retainer 214 causefield-sensitive reticle 212 to be at ground potential at contact point230 at the conductive chromium guard ring of reticle 212. As a result,the voltage contours represented by field contours 224 in FIG. 3 aremore compressed compared to the voltage contours in FIG. 2. This causesa higher voltage gradient within field-sensitive reticle 212 than inreticle 112 of FIG. 2 under otherwise similar conditions.

In accordance with the invention, an electrically-conductive container104 for holding a field-sensitive article 112 with anelectrically-insulating support 110 within the container is typicallylocated in a controlled environment within a chamber 130 defined byboundary walls 132, as depicted in FIG. 1. When a container 104 is opento move a field-sensitive article into or out of container 104,typically an ionizer 140 is utilized to neutralize electric chargeslocated within chamber 130 and enclosure 108. The term “chamber” is usedbroadly to mean a defined space having finite boundaries that make itpossible for the environment within the space to be controlled to somedesired degree. Typically, boundaries and other structures of acontrolled environment of chamber 130 are maintained at a constantelectrical potential, as indicated by ground connector 142 in FIG. 1. Insome embodiments, electrically-conductive container 104 becomes a partof boundary walls 132, for example, when a SMIF pod is located in a loadport. Then, when the pod opened, the exterior surface of the pod remainsoutside chamber 130, but electrically-conductive container 104 can openwithin environmentally-controlled chamber 130.

FIG. 4 depicts a perspective view 300 of a SMIF pod 302 for holding afield-sensitive reticle in accordance with the invention. FIG. 4 showspod 302 in an open position. FIG. 5 depicts a cross-sectional view 306of pod 302 in a closed position holding field-sensitive reticle 304. Pod302 includes pod bottom 310 and pod top 312. Pod bottom 310 compriseselectrically-conductive lower container wall 314. Pod top 312 includeselectrically-conductive upper container wall 316. In a closed positionas depicted in FIG. 5, upper container wall 316 and lower container wall314 form a continuously electrically-conductive container 320 and defineenclosure 322. In its closed position, continuouselectrically-conductive container 320 functions as a Faraday cage,effectively preventing any electric fields external to container 320from penetrating into enclosure 322. Pod 302 further includes compliantgasket 324 located between pod bottom 310 and pod top 312 to form apressure seal when the pod is in a closed position. Suitable compliantmaterials for gasket 324 are known in the art; for example, vulcanizedrubber, Viton, Chemraz or similar materials. Locks 326A, 326B help toestablish continuous electrical contact between pod bottom 310 and podtop 312 in a closed position, as well as to establish a pressure sealwith compliant gasket 324. Typically, electrically-conductive lowercontainer wall 314 and electrically-conductive upper container wall 316are made only from conductive metal material, such as stainless steel304. Alternatively, container walls 314, 316 comprise insulative orstatic dissipative material that are coated with or are embedded withconductive materials to make container walls 314, 316 sufficientlyconductive. Portion 328 of pod top 306 external to container wall 316typically comprises hard polymer plastic material to minimize weight.Portion 328 of pod top 306 optionally includes an automation flange 329(see FIG. 4) and manual handles 331. In accordance with the invention,SMIF pod 302 further comprises electrically-insulating supports, orrails, 330 made completely from insulative material.Electrically-insulating supports 330 support field-sensitive reticle 304in such manner that reticle 304 does not come into electrical contactwith electrically-conductive container walls 314, 316, which aretypically connected to a constant electrical potential, such aselectrical ground. Pod 302 further comprises electrically-insulatingside retainers 332 and electrically-insulating vertical retainers 334,which are made completely from insulative material. Supports 330 andretainers 332, 334 are preferably made from insulative materials thatwill not abrade or chip the reticle 304, for example a soft polymerplastic, such as nylon or delrin. Acetron GP, an acetyl polymeravailable from GE Polymer, is a suitable insulative plastic typicallyused for making supports 330 and retainers 332, 334. Insulative ceramicmaterials, such as quartz, are also suitable for making supports 330 andretainers 332, 334. Alternatively, when it is not practically feasibleto make supports 330, retainers 332, 334 and other structures withinenclosure 322 completely from insulating material, theseenclosure-internal structures can be made partially from conductive orstatic dissipative material, as long as only insulative surfaces of thestructures are in contact with conductive regions of reticle 304. Asexplained above, protection of a reticle 304 or of some otherfield-sensitive article increases as the amount and proximity ofconductive or dissipative material in enclosure 322 decrease.

Electrically-insulating support 330 preferably comprises substantiallyinsulative material. When support 330 also comprises conductive orstatic dissipative material covered by insulating material at thecontact surfaces with a reticle, then the insulating covering or coatingis typically at least about 2 microns thick. To minimize the compressionof electric field lines if an electric field exists in the environmentof the reticle, there is preferably no conducting or static dissipativematerial within 2 mm of said reticule, and more preferably not within 10mm of said reticule.

Similarly, when locating or moving a reticle within a conductivecontainer or within a controlled environment in accordance with theinvention, conducting or static dissipative material should be kept atleast 2 micron away from said reticule, preferably 2 mm, and morepreferably at least 10 millimeters away.

FIG. 6A depicts a perspective view of a cassette portion 402A of amulti-reticle SMIF pod 402 (not completely shown). FIG. 6B depicts aperspective view of a cover portion 402B of multi-reticle SMIF pod 402(not completely shown). Cassette portion 402A includes pod bottom 410.Pod bottom 410 comprises electrically-conductive container lower wall414. Cassette portion 402A further includes electrically-conductivecontainer sidewalls 416, electrically-conductive container back wall418, and electrically-conductive container upper wall 420. As depictedin FIG. 6B, cover portion 402B comprises movable electrically-conductivefront container wall 422 and electrically-conductive rear panel-walls424. When cassette portion 402A and cover portion 402B are lockedtogether in their closed position, electrically-conductive walls 414,416, 418, 420, 422, and 424 form a continuous, integral conductivecontainer wall that defines an enclosure 426 (indicated in FIG. 6A),which corresponds to the space in which field-sensitive reticles 430,electrically-insulating supports 432, and electrically-insulating sideretainers 434 are enclosed. Supports 432 and retainers 434 are fastenedto insulative stanchions 436, which are integrally connected toinsulative mounting strips 437. Mounting strips 437 are attached,typically with screws, to the inside surfaces of conductive containersidewalls 416. Cassette portion 402A further includes compliant gasket440 located along the outer edge of lower container wall 414. Gasket 440helps to form a pressure seal between cassette portion 402A and coverportion 402B when pod 402 is in a closed position. Locks 446A, 446B helpto establish continuous electrical contact between cassette portion 402Aand cover portion 402B when pod 402 is in a closed position, as well asto establish a pressure seal with gasket 440. Typically,electrically-conductive container walls 414, 416, 418, 420, 422, and 424are made only from conductive metal material, such as stainless steel304. In certain preferred embodiments, one or more of the conductivewalls, particularly movable front wall 422 and rear panel-walls 424, aremade from transparent insulative glass or plastic, which are coated witha transparent conductive metal oxide. Alternatively, the insulativeglass or plastic contains an embedded metal mesh that does notsignificantly reduce the optical transparency. Pod top 450 of coverportion 402B typically comprises hard polymer plastic material tominimize weight. Pod top 450 optionally includes an automation flangeand manual handles.

In accordance with the invention, electrically-insulating supports 432and side retainers 434 of cassette portion 402A, as well as theirsupporting structures 436, 437, which fasten structures 430,432 toelectrically-conductive sidewalls 416, are made completely frominsulative material, typically from an insulative plastic, such asAcetron GP. In certain embodiments, supports, retainers, and othersupporting structures are made with an insulative ceramic, such quartz.Optionally, the surfaces of ceramic supports 432 and retainers 434 thatcome into contact with reticles 430 are coated with a thin film ofinsulative plastic to provide a soft smooth surface.

Pod 402 includes an advancing retainer mechanism comprising advancingretainer 460, depicted in FIG. 6B. When pod cover portion 402B is in aclosed and locked position covering cassette portion 402A,electrically-insulating advancing retainer 460 is advanced toward frontedge 462 and comes to rest substantially in contact with forward edges464 of reticles 430. Preferably, advancing retainer 460 is madesubstantially from only insulating material. Advancing retainer 460 isaligned so that the advancing surface of retainer 460 that comes to restagainst the edges 464 of reticles protrudes from the plane of conductivecontainer wall 422. As depicted in FIG. 6B, conductive front wall 422comprises a transparent conductive wall portion, namely, conductivetransparent window 468. Thus, movable front wall 422 includes conductiveconductive transparent window 468 and conductive sheet 470. Coverportion 402B includes transparent front panel 472, typically comprisingtransparent plastic, which does not advance and is not a part of theFaraday cage. Advancing retainer 460 typically comprises insulativeplastic, such as Acetron GP. Conductive sheet 470 typically comprises asheet of conductive metal, such as stainless-steel-304 or aluminum-6061,that is clamped or otherwise fastened to advancing retainer 460 usingconventional techniques. Movable conductive front wall 422 does not comeinto physical or electrical contact with field-sensitive reticles 430when pod cover portion 402 is in its closed position with advancingretainer 460 typically being in physical contact with field-sensitivereticles 430. Preferably, movable conductive front wall 422 comes intoclose proximity with conductive edges 462 and with conductive lower wall414, but preferably does not make physical contact (to avoid creatingparticles). When a surface of conductive front wall 422 that comes atleast within 10 mm of a corresponding opposing surface of edge 462 orlower wall 414, then this proximity typically provides a sufficientlycontinuous integral portion of a conductive container. To achieve aclose fit of front wall 422 to adjoining conductive surfaces at edges462 or container bottom 414, sheet edges 484 typically are curvedinwards.

FIG. 7 depicts schematically a cross-sectional view 500 of a system 502in accordance with the invention. System 502 includes boundary walls 504that define a chamber 506 having a controlled environment. An electricalconnector 507 connects boundary walls 504 to electrical ground or someother fixed potential. Boundary walls 504 often include a transparentportion. The controlled environment of system 502 may be any one of avariety of controlled environments in a fab; for example, a chamber in amanufacturing processing tool or simply a controlled environment betweenload ports of two SMIF pods. System 502 further includes a load port 508for holding and operating a SMIF pod and a SMIF pod 510. SMIF pod 510 isdepicted in closed position in FIG. 7. When pod 510 is located in loadport 508, it is electrically connected by electrical connector 509 toboundary walls 504 and thereby to electrical ground (or some other fixedpotential) through connector 507. Preferably, electrical connector 509is resistive to prevent a rapid electrical discharge in case pod 510 ischarged before it is loaded into load port 508. In accordance with theinvention, SMIF pod 510 comprises conductive container 512 andelectrically-insulating supports 514 for supporting a field-sensitivearticle 516 so that article 516 does not come into electrical contactwith electrically conductive container 512. SMIF pod 510 also compriseselectrically-insulating aligners 517 and electrically-insulatingvertical retainers 518. Typically, system 502 includes one or moreinternal panels 519 within chamber 506. In accordance with theinvention, internal panels 519 and the ancillary stanchions and otherstructures supporting them within chamber 506 preferably are madesubstantially completely from insulative material. The term “internalpanel” is used in a general sense to mean any one or several of avariety of structures present in controlled environments of fabs. Themeaning of “internal panel” includes, for example: a support rail forsupporting a field-sensitive or other article within chamber 506;structures for segregating areas for contamination control; panels forcontrolling fluid flow within chamber 506; and panels for directing theflow of ions to target locations in chamber 506. FIG. 8 shows aschematic view 520 of system 502 in which SMIF pod 510 is in an openposition within the controlled environment of chamber 506. As depictedin FIG. 8, system 502 further comprises an effector 522 for moving afield-sensitive article within chamber 506 to or from opened SMIF pod510. Effector 522 preferably is made completely from insulativematerial. In certain embodiments, effect of 522 is made from insulativeceramic material, and is optionally coated with an insulative plasticcoating to minimize abrasion. Effector 522 is typically an end effectorof a robot arm or a manually operated effector. It is depicted beneathreticle 516 and supporting it under gravity, but it could equally wellgrip a reticle from the sides or hold a reticle by vacuum applied to thereticle's top surface. As depicted in view 520 of FIG. 8,field-sensitive article 516, such as a reticle, is located in chamber506 on effector 522, which has removed the article from supports 514.Alternatively, insulative structure 522 is a chamber-internal supportfor field-sensitive article 516. It is possible for a field-sensitivearticle 516 to be carrying an electrical charge. FIG. 9 shows a view 530depicting field lines 532 of an electric field in a system 502 betweenan electric charge 531 on article 516 and boundary walls 504 when theboundary walls are at a different electrical potential, for example, atelectrical ground. Because effector 522 and internal panels 519 are madefrom insulative material in accordance with the invention, the electricfield is not compressed within chamber 506, as indicated by the longfield lines 532. In preferred embodiments in accordance with theinvention, as depicted in view 540 of FIG. 10, a system 502 comprises anionizer 542 for neutralizing electrical charges within chamber 506, inparticular, static electrical charges on a field-sensitive article 516and on insulative panels 519 and other internal structures, includingthe insulative structures within the container 510 when it is opened.

FIG. 11 depicts a cross-sectional view 600 of a conventional system 602of the prior art that includes an effector 622 that is not in accordancewith the invention. Effector 622 comprises conductive or staticdissipative material that is at a controlled potential, such as groundpotential. As a result, an electric field exists between the electriccharge on article 616 and effector 622. The dense electric field,indicated by short field lines 624, has a high field strength that ishazardous to a field-sensitive article 616.

FIG. 12 depicts a cross-sectional view 700 of a conventional system 702of the prior art that includes internal panels 719 that are not inaccordance with the invention. Internal panels 719 comprise conductiveor static dissipative material that is at a controlled potential, suchas ground potential. As a result, an electric field exists between theelectric charge on article 716 and panels 719. The dense electric field,indicated by short field lines 724, has a high field strength that ishazardous to a field-sensitive article 716.

The particular systems, designs, methods and compositions describedherein are intended to illustrate the functionality and versitility ofthe invention, but should not be construed to be limited to thoseparticular embodiments. Systems and methods in accordance with theinvention are useful in a wide variety of circumstances and applicationsto control and reduce electric-field-induced damage to field-sensitivearticles, especially in semiconductor fabs. It is evident that thoseskilled in the art may now make numerous uses and modifications of thespecific embodiments described, without departing from the inventiveconcepts. It is also evident that the steps recited may, in someinstances, be performed in a different order; or equivalent structuresand processes may be substituted for the structures and processesdescribed. Since certain changes may be made in the above systems andmethods without departing from the scope of the invention, it isintended that all subject matter contained in the above description orshown in the accompanying drawing be interpreted as illustrative and notin a limiting sense. Consequently, the invention is to be construed asembracing each and every novel feature and novel combination of featurespresent in or inherently possessed by the systems, methods andcompositions described in the claims below and by their equivalents.

1. An apparatus for holding a field-sensitive article comprising: aconductive container having an electrically-conductive container wallsaid container wall defining an enclosure; and anelectrically-insulating support located within said enclosure, saidelectrically-insulating support configured for supporting afield-sensitive article within said enclosure without electricallycontacting said electrically-conductive container wall; there being nosignificant source of microwave energy within said enclosure.
 2. Anapparatus as in claim 1 wherein said electrically-conductive containerwall comprises substantially only conductive material.
 3. An apparatusas in claim 1 wherein said electrically-conductive container wallcomprises substantially only metal.
 4. An apparatus as in claim 1wherein said electrically-conductive container wall comprisessubstantially stainless steel.
 5. An apparatus as in claim 1 whereinsaid electrically-insulating support comprises substantially onlyinsulative material.
 6. An apparatus as in claim 1 wherein saidelectrically-insulating support comprises ceramic material.
 7. Anapparatus as in claim 1 wherein said electrically-insulating supportcomprises polymer plastic.
 8. An apparatus as in claim 1 wherein acontrolled electrical potential is connected to said conductivecontainer.
 9. An apparatus as in claim 1 wherein an electrical connectorconnects said conductive container to a controlled electrical potential.10. An apparatus as in claim 9 wherein said electrical connectorcomprises one from a group consisting of an electrical conductor and astatic dissipative material.
 11. An apparatus as in claim 1 wherein saidconductive container comprises a portion of a SMIF pod.
 12. An apparatusas in claim 11 wherein said electrically-insulating support isconfigured for supporting a reticle.
 13. An apparatus as in claim 11wherein an ionizer is located external to said enclosure forneutralizing an electric charge.
 14. An apparatus as in claim 11 whereina portion of said electrically-conductive container wall issubstantially transparent.
 15. A system for handling a field-sensitivearticle, said system having boundary walls, a chamber defined by saidboundary walls, a load port for holding and operating a SMIF pod, a SMIFpod, and an effector for moving an article within said chamber to orfrom an open SMIF pod, wherein: said SMIF pod a conductive container andan electrically-insulating support located within said conductivecontainer, said electrically-insulating support configured forsupporting a field-sensitive article without electrical contact to saidconductive container; and said effector being an electrically-insulatingeffector configured for moving a field-sensitive article.
 16. A systemas in claim 15 wherein said electrically-insulating chamber-internalsupport is configured for supporting a field-sensitive article withinsaid chamber without electrical contact to said boundary walls.
 17. Asystem as in claim 16 wherein said electrically-insulatingchamber-internal support comprises substantially only insulativematerial.
 18. A system as in claim 15 having an internal panel locatedwithin said chamber wherein said internal panel is anelectrically-insulating internal panel.
 19. A system as in claim 18wherein said electrically-insulating internal panel comprisessubstantially only insulative material.
 20. A system as in claim 15wherein said boundary walls are substantially electrically conductive.21. A system as in claim 15 wherein said boundary walls comprisesubstantially only electrically conductive material.
 22. A system as inclaim 15 wherein said boundary walls comprise static dissipativematerial.
 23. A system as in claim 15 wherein said boundary walls areconnected to a controlled electrical potential.
 24. A system as in claim15 wherein said electrically-insulating support is configured forsupporting a reticle and said effector is configured for moving areticle.
 25. A system as in claim 15 wherein an ionizer is locatedwithin said chamber for neutralizing an electric charge.
 26. A system asin claim 15 wherein a portion of said boundary walls is substantiallytransparent.
 27. A system for handling a field-sensitive article, saidsystem having boundary walls, a chamber defined by said boundary walls,and a container within said chamber for holding a field-sensitivearticle, wherein: said container comprises an electrically-conductivecontainer wall, said container wall defining an enclosure; anelectrically-insulating support located within said enclosure, saidelectrically-insulating support configured for supporting afield-sensitive article within said enclosure without electricallycontacting said electrically-conductive container wall; and an ionizerfor providing charge-neutralizing ions in said chamber.
 28. Anelectrically-insulating support for a reticle, said support having aninsulating member wherein there is no conducting or static dissipativematerial close enough to said reticule to cause a concentration ofelectrical field lines sufficient to cause field-induced damage.
 29. Anelectrically-insulating support as in claim 28 wherein there is noconducting or static dissipative material within 2 microns of saidreticule.
 30. An electrically-insulating support as in claim 28 whereinthere is no conducting or static dissipative material within 2 mm ofsaid reticule.
 31. An electrically-insulating support as in claim 28wherein there is no conducting or static dissipative material within 10mm of said reticule.
 32. A method of avoiding field-induced damage of afield-sensitive article by holding said field-sensitive article with anelectrically-insulating support located within an enclosure defined byan electrically-conductive container wall of a conductive container sothat said field-sensitive article does not electrically contact saidelectrically-conductive container wall and is not exposed to anysignificant source of microwave radiation.
 33. A method as in claim 32of: locating said conductive container in a chamber having a controlledenvironment; generating ions in said controlled environment in saidchamber; and opening said conductive container in said controlledenvironment.
 34. A method as in claim 32 of: locating said conductivecontainer in a chamber having a controlled environment; opening saidconductive container in said controlled environment; and moving saidfield-sensitive article out of said conductive container into saidcontrolled environment using an electrically-insulating effector.
 35. Amethod of protecting a field-sensitive reticule from electric-fieldinduced damage, by keeping all conductive or static dissipative materialfar enough away from said reticule to prevent a concentration ofelectrical field lines sufficient to cause field-induced damage to saidreticle.
 36. A method as in claim 35 wherein said protecting is keepingsaid conducting or static dissipative material at least 2 microns awayfrom said reticule.
 37. A method as in claim 35 wherein said protectingis keeping said conducting or static dissipative material at least 2 mmaway from said reticule.
 38. A method as in claim 35 wherein saidprotecting is keeping said conducting or static dissipative material atleast 10 mm away from said reticule.